Assessing energy savings potential of Personalised Environmental Comfort Systems (PECS) in air-conditioned environment

Personalised Environmental Comfort Systems (PECS) are increasingly considered for enhancing energy efficiency in buildings by providing individualized thermal comfort. However, while the comfort benefits of PECS are well documented, its energy saving potential remains unclear and has often been assessed through subjective applications. This study aims to clarify the energy savings that can be achieved with PECS, particularly when used alongside traditional heating, ventilation and air conditioning (HVAC) systems.

The research focuses on the dynamic relationship between PECS and conventional HVAC systems, investigating how their interaction during the operational phase affects both energy use and occupant comfort. A comprehensive methodological framework is presented, consisting of several steps. First, the identification of systems used for personal climate control and the background environment is addressed, specifying their types, heat transfer mechanisms and control volumes.

Next, the operating range of the control and manipulation variables on which both systems can act is identified. Finally, a parametric analysis assesses the potential energy savings that can be achieved through various combinations of selected variables, compared to a baseline scenario without PECS. This analysis generates a performance map that links energy savings with achieved comfort levels. This methodology can be supported by both experimental studies and numerical simulations, utilizing customized models for PECS and established dynamic simulation software for the evaluation of background environment with traditional HVAC.

A detailed case study demonstrates the application of this methodology, using a convective PECS for both heating and cooling, integrated with a traditional all-air HVAC system installed in a single office room. Based on a numerical model, the procedure was rigorously tested, resulting in a parametric map that highlights the energy savings expressed in terms of final electricity saved compared to a baseline scenario without PECS. This analysis revealed both advantageous and disadvantageous conditions: optimal scenarios where the use of PECS leads to significant energy savings without compromising comfort, and less favorable scenarios where excellent comfort is achieved at a high energy cost. A preliminary experimental validation of the findings has been also carried out in a thermostatic chamber.

The results underline the importance of correctly implementing PECS to maximize energy efficiency while maintaining occupant comfort. Misapplication could result in unnecessarily high energy usage. Thus, the study not only provides insights into optimizing the integration of PECS with HVAC systems but also identifies specific conditions under which PECS can be most effectively utilized, stimulating sustainable building practices.